In recent years, it has become clear that diglycerides have an anti-obesity action, weight-gain suppressing action and the like (Japanese Patent Laid-Open No. Hei 4-300828). There has been an attempt to incorporate them in various foods. It is reported that edible oil-in-water type emulsified compositions having a rich fatty savor and good taste are available even at a lowered fat content by using, as an oil phase, a glyceride mixture having a high diglyceride content (Japanese Patent Laid-Open No. Hei 3-8431).
It has however been revealed that acidic oil-in-water type emulsified compositions such as mayonnaise obtained by emulsifying an oil phase having a high diglyceride content with an egg yolk causes problems, after storage, such as oil/water separation and deterioration in appearance such as loss of gloss. With a view to overcoming these problems, a technique of adjusting a lysophospholipid content in an acidic oil-in-water type emulsified composition is reported (Japanese Patent Laid-Open No. 2001-138).
Another problem upon preparation of acidic oil-in-water type emulsified compositions such as mayonnaise is that when they are transferred from an emulsifying machine to a filling machine via a pipe or they are filled in a container, shear occurs by pressure, causing a change in the physical properties of the acidic oil-in-water type emulsified compositions such as viscosity. Whenever acidic oil-in-water type emulsified compositions, for example, mayonnaise filled in a plastic mayonnaise bottle is used, a pushing pressure is applied to the bottle, which is prone to cause emulsion breakage, water/oil separation and the like, thus deteriorating their quality. Acidic oil-in-water type emulsified compositions are therefore desired to have stability against pressure-induced shear stress which occurs upon preparation, filling or actual use.
The above-described technique of improving appearance by adjusting a lysophospholipid content is effective when the composition is stored statically, but its effect is not sufficient in the presence of pressure-induced shear stress.